Problem with values in a text box flash 8 (as2)

Hi , can you help me please?
I have a text box in which the user can add only numbers, in my program also i have a static text box in which a have written a text.
The problem is that every character used in the static text box , is recognize as input in my input text box and the result is NaN.
Can anyone help me with this?
I have embeded in my input text box Numerals [0…9]